Swellable downhole packers

ABSTRACT

A swellable packer including a tubular member and a swellable element. The tubular member is disposable on a mandrel configured to be deployed into a wellbore. The swellable element is disposed around the tubular member, and has a first region comprising a swellable material and a second region comprising a degradable or dissolvable material.

FIELD

The subject disclosure generally relates to downhole packers for forminga seal in an annulus. More particularly, the subject disclosure relatesto an improved swellable downhole packer.

BACKGROUND

Hydrocarbons are produced from a wellbore that passes through one ormore hydrocarbon producing formations.

A packer is a device that is used in a well to form an annular sealbetween an inner tubular member and a surrounding outer tubular member(a casing string or a liner, as just a few examples) or borehole wall.

Swellable packers are often used to isolate sections of the wellborefrom one another, particularly those sections adjacent differenthydrocarbon producing formations. Control of the swellable packers swellrate, swell percentage, and the relative hardness of the swellableelement is important to assure sufficient engagement with the wellborewall, and thus efficient isolation of the desired sections of thewellbore.

There exists a need for swellable elements and methods for makingswellable elements that have controlled swell rates and increased swellpercentages.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In an embodiment, a packer usable within a wellbore is disclosed. Thepacker comprises a tubular member, a swellable member circumferentiallydisposed about an axis of the tubular member which is adapted to swellin the presence of a triggering agent to form an annular seal in thewellbore. The swellable member comprises a first region comprising aswellable material and a second region comprising a degradable ordissolvable material.

In an embodiment, an annular seal is formed using a swellable memberlongitudinally extending along a tubular member in a wellbore. Theswellable member comprises a first region comprising a swellablematerial, a second region comprising a degradable or dissolvablematerial. The swellable material is adapted to swell in the presence ofa triggering agent to form the annular seal in the wellbore.

In other embodiments, a system usable within a well is disclosed. Thesystem comprises a tubing string to extend downhole in the well and apacker to form an annular seal between the tubing string and a casing orwellbore wall. The packer comprises an inner core and a swellable bodymounted to the inner core to swell to form an annular seal in the well.The swellable body comprises a first region comprising a swellablematerial and a second region comprising a degradable or dissolvablematerial.

Further features and advantages of the subject disclosure will becomemore readily apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject disclosure is further described in the detailed descriptionwhich follows, in reference to the noted plurality of drawings by way ofnon-limiting examples of the subject disclosure, in which like referencenumerals represent similar parts throughout the several views of thedrawings, and wherein:

FIG. 1 depicts a schematic of a conventional swellable packer in aborehole;

FIG. 2 depicts a schematic of a conventional swellable packer setting inan irregular open hole;

FIG. 3 depicts a swellable packer comprising a laminate structure;

FIG. 4 depicts a graph of the swelling kinetics for a conventionalswellable packer and packers with laminate structures as described inthe subject disclosure;

FIG. 5 depicts a swellable packer comprising a laminate structuresetting in an irregular borehole, e.g., open hole borehole;

FIG. 6A depicts a swellable packer comprising a laminate structure andan external coating; and

FIG. 6B depicts a swellable packer comprising inner layers of swellablematerial and outer layers of a laminate structure; and

FIGS. 7A and 7B depict a swellable packer comprising a laminatestructure and degradable or dissolvable material. The degradablematerial in the laminate structure is replaced in sections with voids inFIG. 7A and with porous polymers in FIG. 7B.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the examples of the subject disclosure onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the subject disclosure. In this regard, no attemptis made to show structural details in more detail than is necessary, thedescription taken with the drawings making apparent to those skilled inthe art how the several forms of the subject disclosure may be embodiedin practice. Furthermore, like reference numbers and designations in thevarious drawings indicate like elements.

Swellable packers are existing commercialized technology in the oil andgas industry. Swellable packer systems are generally composed of atleast three components including a swellable element, a base tubular(e.g., base pipe), and rigid end rings. The swellable element is made ofan elastomer that imbibes solvent from the surroundings and expandsautomatically. The tubular or base pipe may be production tubing oranother tubular member. The purpose of the packer is to form a sealbetween this tubular and the casing/formation. Therefore, a certainamount of contact pressure can build up to resist the penetration ofliquid from a high-pressure end to a low-pressure end.

The swellable packers that are disclosed herein may take on numerousforms, depending on the particular implementation. As non-limitingexamples, in accordance with example implementations, the swellablepackers may be gravel packing packers, zonal isolation packers, bridgeplugs, and so forth. The swellable packers may be used to form sealsinside tubular members, such as casing strings and liners, and may beused to seal against uncased wellbore walls, depending on the particularimplementation. The swellable packers that are disclosed herein may beused in a wide variety of downhole operations, such as gravel packingoperations, stimulation operations, fracturing operations, productionoperations, perforating operations, injection operations, testingoperations, and so forth. Moreover, the swellable packers that aredisclosed herein may be used in temporary workover operations (testing,stimulation and perforating operations, for example), as well as inpermanent completions.

In an embodiment, composites of laminate structures comprising swellableelastomer and degradable/dissolvable polymers are used in swellablepackers. This composite structure replaces the isotropic and homogenousbulk material used in conventional swellable packers. The advantages ofusing composites of laminate structures include the ability to optimizethe kinetics of swelling, i.e., a first rate which is slow before thedegradable/dissolvable polymers degrade or dissolve and a second ratewhich is faster than the first rate after the degradable/dissolvablepolymers degrade or dissolve. In addition, the sealing capability canalso be improved for irregular open holes since each layer of swellablematerial is isolated and therefore can swell to different swellingratios to fit the borehole.

FIG. 1 depicts a schematic of a conventional packer in a borehole. InFIG. 1, the swellable packer 101 includes a member 105 which isgenerally tubular, so that fluid may pass through the bore of the setpacker. The member 105 can be a downhole tubular such as a pipe or amandrel, which can be configured to be deployed into a wellbore. Themember 105 can also be configured to connect to one or more otherdownhole members. Accordingly, the member 105 can be incorporated into acompletion string, a workstring, or another downhole string. Theswellable packer 101 can be used in cased or uncased wellbore. Along asubstantial length of this member 105, a swellable elastomericsleeve-shaped body 109 is positioned over the exterior surface of themember 105. This swellable body is designed to swell in response to atrigger so that swelling creates a seal between the member 105 and theinterior surface of either the wellbore or the casing. Initially, theswellable packer 101 is deployed downhole in its unset state, whichmeans the swellable body 109 is radially contracted, i.e., the swellablebody 109 has not or at least has not significantly swollen while thetubing string 105 is being run into the wellbore as the swellable body109 has not yet been exposed for a sufficient time to a triggeringagent. After the member 105 is appropriately positioned in the wellbore,the swellable packer 101 is set, which means that the swellable body 109swells to radially expand so that the swellable body 109 forms anannular seal against the interior surface of the surrounding casingstring or wellbore.

The trigger may be any available device or physical parameter known tothose of skill in the art to initiate the swelling or expansion of theelastic material, and may include one or more of the following: fluid,gas, temperature, pressure, pH, electric charge, or chemicals.Illustrative fluid triggers include water, hydrocarbons, treatmentfluids, or any other fluid known to those skilled in the art. To limitaxial movement of the swellable elastomeric body 109 as it radiallyswells, the packer is provided with end caps or metal rings 103 at eachend, with each end being positioned over the exterior surface of themember 105 and secured to the tubular member 105.

The swellable elastomeric sleeve-shaped body 109 includes material thatwill react with one or more triggers to volumetrically expand orotherwise swell. Non-limiting examples of oil swellable materials thatcan be used to make at least a portion of body 109 include polyisoprene,polyisobutylene, polybutadiene, natural rubber, polystyrene,poly(styrene-butadiene), polychloroprene, polysiloxane,poly(ethylene-propylene), ethylene propylene diene monomer rubber(EPDM), ethylene vinyl acetate (EVA) rubber, chorosulfonatedpolyethylene, epichlorohydrin rubber (ECO), polyacrylic rubber (ACM),ethylene acrylic rubber (AEM), silicone rubber such as VMQ, and/orprecursors, mixtures, or derivatives thereof. Non-limiting examples ofwater swellable materials that can be used to make at least a portion ofbody 109 can include poly(acrylic acid), poly(acrylic acid) potassiumsalt, poly(acrylic acid) sodium salt, poly(acrylic acid-co-acrylamide),poly(acrylic acid-co-acrylamide) potassium salt, poly(acrylicacid-co-acrylamide) sodium salt, poly(acrylic acid) sodiumsalt-graft-poly(ethylene oxide), poly(isobutylene-co-maleic acid) sodiumsalt, poly(methacrylic acid), poly(methacrylic acid) sodium salt,poly(2-hydroxyethyl methacrylate), poly(2-hydroxypropyl methacrylate)and/or precursors, mixtures, or derivatives thereof.

Swellable packers have many advantages when compared to mechanicalpackers which include low cost, no moving parts, and automaticactuation. A disadvantage of current swellable packers is the lack ofcontrol on the actuation time. As shown in FIG. 1, once the geometry ofthe swellable packer 101 and the borehole size are fixed, the actuationtime depends monotonically on a diffusion rate of liquid inside theswellable elastomer. Too fast or too slow of a diffusion rate may createdifficulties. If the diffusion rate is fast, the swellable packer may bestuck in an undesired location, while if the diffusion rate is slow, theactuation time may be long and the operational costs tend to increase.

Another disadvantage of the conventional swellable packer is the sealingcapability of this type of packer in an irregular open hole. In thistype of borehole, the diameter of the borehole varies with depth asshown in FIG. 2. FIG. 2 depicts a conventional swellable packer 201 inan uncased open hole wellbore. The swellable packer 201 includes atubular member 205.

The swellable packer is provided with end caps or metal rings 209 ateach end. FIG. 2 depicts the irregularity of the wellbore and when theswellable packer 201 is in contact with the narrow region of theborehole, stress concentration will generate and prohibit the furtherswelling of the swellable packer 201. To improve the sealing capabilityof these conventional packers one approach is to use softer elastomersbut the mechanical properties will deteriorate for those swellablepackers.

In an embodiment of the subject disclosure, the bulk elastomericmaterial 109 is substituted with a composite material with a laminatestructure comprising swellable materials and degradable or dissolvablematerials as shown in FIG. 3. The term laminate material is used todefine the microstructure of a special type of composite material, i.e.,laminate composite. In such a composite, different phases form aperiodically layered structure. A laminate composite is a material withproperties that vary in only one direction and that direction is calleda laminate direction. This design lends itself to having an increasedcontrol of swelling kinetics. In non-limiting examples, the rate ofswelling is decelerated before the degradable or dissolvable materialsdegrade or dissolve respectively and the rate of swelling is acceleratedonce the degradable or dissolvable material has degraded or dissolved.

The migration of the liquid inside the swellable material can begoverned via a diffusion equation:

$\begin{matrix}{{\frac{\partial c}{\partial t} = {D{\nabla^{2}c}}},} & (1)\end{matrix}$

where c is the volume fraction of liquid and D is the diffusioncoefficient that depends on the material properties of an elastomer andliquid. See Tanaka, T., and Fillmore, D. J., (1979) “Kinetics ofswelling of gels,” Journal of Chemical Physics 70(03): pp. 1214-1218.

As shown in FIG. 4, the volume increment versus time is a continuouscurve and actuation time is on the order of W²/D, where W is thedistance between the tubing and borehole. There is no control on thekinetics of swelling in situations where the geometries of a packer anda borehole are fixed and the downhole fluid is known.

In an embodiment of the subject disclosure, a laminate compositestructure replaces the bulk swellable elastomer used in traditionalswellable packers as depicted in FIG. 2. This material compriseslaminated swellable elastomers 307 and degradable/dissolvable polymers305 as depicted in FIG. 3. The swellable packer 301 includes a tubularmember 309 and is provided with end caps or metal rings 303 at each end.The time for the degradable material to dissolve may be controlled usingdifferent degradable material. Prior to the degradable materialdissolving or degrading, the degradable material prohibits swelling ofthe swellable elastomer as the layers of degradable/dissolvable andswellable material are bonded together.

Therefore, initially the composite material swells slowly as shown inFIG. 4. As the degradable material layer disappears, the surface areafor the swellable material increases significantly when compared to aconventional swellable packer. The characteristic length for diffusionbecomes Δh<<W and the length of swelling will increase quadratically.For example, in a wellbore with W about 3 inches, the actuation time canbe reduced to 1 hour if Δh is taken to be about 0.3 inches. Thiscompares to an actuation time for a conventional swellable packer ofabout 100 hours. Therefore, in embodiments of the subject disclosure,the kinetics of swelling are slow at the beginning and increase in speedas the degradable material layer disappears.

In an embodiment, the swellable packer can seal an irregular open holewithout sacrificing the mechanical properties. As depicted in FIG. 5, aswellable packer 501 is in an uncased open hole wellbore. The swellablepacker 501 includes a tubular member 507. The swellable packer isprovided with end caps or metal rings 505 at each end. FIG. 5 depictsthe irregularity of the wellbore and the swellable packer 501 in contactwith the narrow region of the borehole. Because the swellable layers ofthe laminate structure 503 are isolated from each other, they can swellto different swelling ratios without generating the stress concentrationas depicted in FIG. 5.

In other embodiments, dissolvable/degradable polymer material may becoated on the outside of the laminate structure as depicted in FIG. 6A.As depicted in FIG. 6A, a swellable packer 601 is situated in an uncasedopen hole wellbore. The swellable packer 601 includes a tubular member611. The swellable packer is provided with end caps or metal rings 609at each end. As depicted in FIG. 6A, the laminate structure comprisingswellable 603 and degradable material 605 is coated with a layer ofdegradable material 607. This structure will further control thekinetics of swelling. In other embodiments, as depicted in FIG. 6B, aconventional swellable packer 615 comprises an inner swellable layer 613and an external layer of material comprising a laminate structure ofdegradable material 605 and swellable 603 material, which controls thekinetics of swelling.

In non-limiting examples, the degradable/dissolvable material includedegradable polymers synthesized from mineral origins: aliphaticpolyesters (e.g., polylactic acid, polyglycolic acid, polybutylenesuccinate, polycaprolactone); aromatic polyesters or blends of the twotypes (e.g., polybutylene succinate terephthalate); polyamides;thermoplastic elastomers; polyvinylalcohols; modified polyolefins(polyethylene or polypropylene with specific agents sensitive totemperature or light). In other embodiments, blends and copolymers ofthese polymers and their derivatives may be used. Degradable biopolymersfrom natural origins are also suitable, including six sub-groups:polysaccharides (e.g., starch, cellulose, lignin, chitin); proteins(e.g., gelatine, casein, wheat gluten, silk and wool); lipids (e.g.,plant oils including castor oil and animal fats); polyesters produced bymicro-organism or by plants (e.g., polyhydroxy-alcanoates,poly-3-hydroxybutyrate); polyesters synthesized from bio-derivedmonomers (polylactic acid); and miscellaneous polymers (natural rubbers,composites). In addition, a broad range of dissolvable polymers aresuitable. Depending on the swelling solvent, oil soluble polymers andwater soluble polymers are selected. Oil soluble polymers includeun-crosslinked polyisoprene, polyisobutylene, polybutadiene, naturalrubber, styrene-butadiene copolymer, polyethylene and polypropylene (lowmolecular weight), ethylene-propylene copolymer,ethylene-propylene-diene monomer (EPDM) rubber, polydimethylsiloxane,polyurethane, ethylene vinyl acetate (EVA) rubber, chorosulfonatedpolyethylene, epichlorohydrin rubber (ECO), polyacrylic rubber (ACM),ethylene acrylic rubber (AEM), silicone rubber such as VMQ, etc. Watersoluble polymers include polyethylene glycol, polypropylene glycol,polysaccharides (low molecular weight), hydroxyethylcellulose,carboxymethylcellulose, polyacrylic acid, polymethacrylic acid,polyacrylamide, polymethacrylamide, polyethyleneimine, polyvinyl alcoholand a broad range of water soluble polymers derived from polyvinylalcohol, polyvinyl pyrrolidone, polyoxazoline, etc.

In an embodiment, methods of manufacturing a laminate structure ofswellable material and degradable/dissolvable polymers comprisesassembling alternating sleeves of swellable materials anddegradable/dissolvable polymers on a mandrel. In a non-limiting example,the sleeves are sections of extruded polymer tubes. The laminatestructure can be directly bonded to the mandrel using surface bondingagents, or bonded to a metal insert sleeve which can be placed over amandrel. In non-limiting examples, the layers of swellable materials anddegradable/dissolvable polymers are bonded together using heating ormolding techniques. In an embodiment, methods of manufacturing alaminate structure of swellable material and degradable/dissolvablepolymers include wrapping strips of swellable materials anddegradable/dissolvable polymers over a mandrel to a desired thickness.In a non-limiting example, the strips are manufactured by rubbermilling.

In an embodiment, the layer of degradable/dissolvable polymers coversthe entire surface of the laminate structure as depicted in FIG. 3. Innon-limiting examples, this layer is fabricated by (1) sliding adegradable/dissolvable polymer sleeve; (2) wrappingdegradable/dissolvable polymer strips using a mandrel wrappingtechnique; or (3) spraying a thin layer of degradable/dissolvablepolymer. The usage of these methods depends on thedegradable/dissolvable polymer material and the size of the laminatestructure.

In an embodiment, the swellable materials are wrapped over a mandrel andthe mandrel is placed into a mold with a desired annulus gap size. Themold is then filled with degradable/dissolvable polymers.

In a further embodiment, the degradable/dissolvable polymers arereplaced by voids (no polymer) and a coating as shown in FIG. 7A whichallows for fast sealing applications. FIG. 7A depicts a swellable packer701. The swellable packer 701 includes a tubular member 703. Theswellable packer is provided with end caps or metal rings 705 at eachend. As depicted in FIG. 7A, the structure comprises swellable material711 and voids 707 and is coated with a layer of degradable/dissolvablematerial 709.

In FIG. 7B, the voids are replaced with porous degradable/dissolvablefoam 713. The degradable/dissolvable foam is fabricated by adding ablowing agent to the degradable/dissolvable polymers. There are manyexamples of blowing agents. Non-limiting examples include liquid CO₂,pentane, isopentane, cyclopentane, sodium bicarbonate, or hollow spheressuch as glass shells, epoxide shells, PVDC shells, fly ash, etc. Theelastic properties of the laminate structures can be modified by usingdifferent types of porous polymers. This means the laminate structurescan be made stiffer to sustain more differential pressure or be softerto fit the irregular open hole.

Although only a few examples have been described in detail above, thoseskilled in the art will readily appreciate that many modifications arepossible in the examples without materially departing from this subjectdisclosure. Accordingly, all such modifications are intended to beincluded within the scope of this disclosure as defined in the followingclaims. In the claims, means-plus-function clauses are intended to coverthe structures described herein as performing the recited function andnot only structural equivalents, but also equivalent structures. Thus,although a nail and a screw may not be structural equivalents in that anail employs a cylindrical surface to secure wooden parts together,whereas a screw employs a helical surface, in the environment offastening wooden parts, a nail and a screw may be equivalent structures.It is the express intention of the applicant not to invoke 35 U.S.C.§112, paragraph 6 for any limitations of any of the claims herein,except for those in which the claim expressly uses the words ‘means for’together with an associated function.

What is claimed is:
 1. A packer usable within a wellbore comprising: atubular member; a swellable member circumferentially disposed about anaxis of the tubular member and adapted to swell in the presence of atriggering agent to form an annular seal in the wellbore, wherein theswellable member comprises a first region comprising a swellablematerial; and a second region comprising a degradable or dissolvablematerial.
 2. The method of claim 1, wherein the first region and secondregion are alternated on the tubular member.
 3. The method of claim 1,wherein the swellable member is formed from a laminate compositematerial.
 4. The packer of claim 1, wherein the triggering agent is apredetermined fluid in the wellbore.
 5. The packer of claim 1, whereinthe swellable material is one of an oil swellable material or a waterswellable material.
 6. The packer of claim 1, wherein the first regionand second region are bonded together.
 7. The packer of claim 1, whereinthe swellable member has a first rate of swelling before the secondregion degrades or dissolves; and a second rate of swelling which isfaster than the first rate of swelling after the second region degradesor dissolves.
 8. The packer of claim 1, wherein a surface area of theswellable material increases when the second region degrades ordissolves thus accelerating the rate of swelling.
 9. The packer of claim1, further comprising: a plurality of first and second regions; whereinthe plurality of first regions each swell to different swelling ratiosand conform to a geometry of the wellbore.
 10. The packer of claim 1,wherein the swellable member further comprises: a coating on an outersurface of the swellable member; wherein the coating comprisesdegradable or dissolvable material.
 11. The packer of claim 1, whereinthe degradable or dissolvable material is a porous foam material. 12.The packer of claim 1, wherein the swellable member further comprises: acoating on an inner surface of the swellable member; wherein the coatingcomprises swellable material.
 13. The packer of claim 1, where thedegradable or dissolvable material comprises a plurality of voids. 14.The packer of claim 1, where the degradable or dissolvable material isselected from the group consisting of degradable polymers, degradablebiopolymers, dissolvable polymers; and combinations thereof.
 15. Thepacker of claim 1, wherein the wellbore is an open hole wellbore.
 16. Amethod comprising: forming an annular seal using a swellable memberlongitudinally extending along a tubular member in a wellbore, whereinthe swellable member comprises a first region comprising a swellablematerial; a second region comprising a degradable or dissolvablematerial; and wherein the swellable material is adapted to swell in thepresence of a triggering agent to form the annular seal in the wellbore.17. The method of claim 16, further comprising: degrading or dissolvingthe second region; and increasing a rate of swelling of the firstregion.
 18. The method of claim 16, wherein the first and second regionsare alternatively wrapped about the tubular member.
 19. The method ofclaim 16, wherein the first and second regions are formed from alaminate composite material.
 20. A system usable within a well,comprising: a tubing string to extend downhole in the well; and a packerto form an annular seal between the tubing string and a casing orwellbore wall, the packer comprising: an inner core; and a swellablebody mounted to the inner core to swell to form an annular seal in thewell, the swellable body being mounted to and circumscribing the innercore and comprising: a first region comprising a swellable material; anda second region comprising a degradable or dissolvable material.
 21. Thesystem of claim 20, wherein the swellable member has a first rate ofswelling before the second region degrades or dissolves; and a secondrate of swelling which is faster than the first rate of swelling afterthe second region degrades or dissolves.